Rubber plug for waterproof connector

Abstract: A rubber plug (10) includes a seal portion (11) and an extension portion (15). Inner and outer peripheral lips (12,13) form respective water-tight seals between the rubber plug (10) and a cavity (2), and the rubber plug (10) and a wire (6). The extension portion (15) extends from the seal portion (11) toward an open end of the cavity (2). When a bending force acts on the wire (6), the extension portion (15) slightly deforms elastically, but the seal portion (11) will not be deformed. Therefore, the water-tight condition between the cavity (2) and the wire (6) is maintained. Therefore, even when a bending force acts on the wire (6), water is prevented from intruding into the cavity (2).

Description: This invention relates to a rubber plug that is used in a waterproof connector for forming a water-tight seal between a cavity in the connector housing and an electric wire. An example of a conventional rubber plug is shown in Fig. 4. A rubber plug 30 has a tubular shape as a whole. Annular outer peripheral lips 32 are formed on an outer periphery of the rubber plug, and annular inner peripheral lips 33 are formed on an inner periphery of the rubber plug. The rubber plug 30 is fitted on an electric wire 40 fixedly connected to a rear end portion of a metal terminal 45. The rubber plug is inserted into an open end 43, together with the metal terminal 45 and the wire 40, of a cavity 42 of a connector housing 41. When the rubber plug is thus inserted, the outer peripheral lips 32 are pressed against an inner peripheral surface of the cavity 42, so that a water-tight seal is formed between the rubber plug 30 and the inner surface of the cavity 42. Also, the inner peripheral lips 33 are pressed against an outer peripheral surface of the wire 40, so that a water-tight seal is formed between the rubber plug 30 and the wire 40. With this arrangement, water is prevented from intruding into the cavity 42. Generally, depending on the manner of arranging the wire 40, the wire 40 may be bent laterally at the open end 43 of the cavity 42, as shown in Fig. 5. In such a case, in the above conventional rubber plug 30, a force bending the wire 40 acts on the rubber plug 30, so that the rubber plug 30 is compressed at a region disposed inwardly of this bent portion. Therefore, at the opposite side, that is, at a region disposed outwardly of the bent portion, a gap 44 develops between the outer peripheral lips 32 of the rubber plug 30 and the inner peripheral surface of the cavity 42. This has the undesirable effect of allowing water to enter into the cavity 42. In addition, the wire 40 comes in contact with the sharp edge 50 of the connector, which may cause damage to the wire. US-A-5,147,222, from which the present invention starts from, discloses a sealed electrical connector including an outer shell which is profiled to receive a pin housing therein. The pin housing has mounted therein a plurality of pins. The interior of the housing shell is sealed by placing a plug over the end of a wire and placing a terminal at the wire's end, the plug and wire into the rear of the connector shell. To prevent the ingress of water into the shell, the plug includes at its exterior end an elongate collar or extension which, if the wire is pulled, will compress. This prevents the exterior ribs from pulling away from the aperture allowing the ingress of water. The present invention has as an object to provide a rubber plug for a waterproof connector in which the sealing characteristics are improved over the sealing characteristics of the prior art. According to the present invention, there is provided - in combination with a waterproof connector having a housing that includes a cavity including an inner surface - a rubber plug comprising: a seal portion that contacts the inner surface of the cavity and an exterior surface of a wire disposed within the rubber plug; and an extension portion extending from said seal portion toward an open end of said cavity, wherein a gap is formed between the outer periphery of said extension portion and the inner surface of said cavity. According to the present invention, this rubber plug is furthermore characterized in that said extension portion has a length that projects outwardly from the open end of said cavity. When a bending force acts on the wire, a portion of the extension portion disposed near the open end of the cavity is pressed by the wire at a region disposed inwardly of the bent portion, so that the portion of the extension portion is pressed against the inner surface of the cavity in a compressed manner, and hence is elastically deformed. The extension portion can be thought of as a protective device for absorbing compression forces. At a region disposed outwardly of the bent portion, the extension portion is elastically deformed away from the inner surface of the cavity. Thus, the only portion which is elastically deformed when the bending force acts on the wire is the extension portion, and the bending force acting on the wire will not act on the seal portion, and therefore the seal portion will not be elastically deformed. The inner diameter of the cavity is larger than the outer diameter of the extension portion, so a gap is formed between the extension portion and the inner surface of the cavity. Accordingly, when the rubber plug is inserted into the cavity, no frictional resistance will develop between the extension portion and the inner surface of the cavity. In addition, the wire may extend from the end of the extension portion projected outwardly beyond the open end of the cavity, and, therefore, even when a bending force acts on the wire to bend the wire to a large extent, the wire will not engage an edge of the open end of the cavity. With this construction, the gap is provided between the extension portion, extending toward the open end of the cavity, and the inner surface of the cavity. Therefore, a rubber plug or rubber body is provided for establishing a waterproof connection in which the metal terminal inserting operation will not be affected. Even when a bending force acts on the wire, a waterproof seal is maintained. In addition, deformation of the seal portion is prevented, thus further enhancing the sealing function. The invention will now be described in more detail with reference to the following drawings, wherein: Fig. 1 is a cross-sectional view of a waterproof plug in accordance with a first embodiment of the invention; Fig. 2 is a cross-sectional view of the first embodiment, showing a wire in a bent condition; Fig. 3 is a cross-sectional view of a second embodiment; Fig. 4 is a cross-sectional view of a conventional example; and Fig. 5 is a cross-sectional view of the conventional example, showing a wire in a bent condition. A first preferred embodiment of the present invention will now be described with reference to Figs. 1 and 2. A cavity 2 in a connector housing 1 of a waterproof connector is shown in cross-section in Figs. 1 and 2. A metal terminal 5 and an electric wire 6, which is connected to a rear end portion of the metal terminal, are inserted into the cavity 2. A waterproof rubber plug or body 10 is fitted on an outer periphery of that portion of the wire 6 disposed immediately after the position where the wire 6 and the metal terminal 5 are connected together. The rubber plug 10 serves to prevent water from intruding through an open end 3 of the cavity 2, where the metal terminal 5 is located. The rubber plug 10 is fitted on the wire 6, and, in this condition, the rubber plug 10 is inserted, together with the metal terminal 5 and the wire 6, into the cavity 2. The rubber plug 10 is made of an elastic rubber material, and comprises a seal portion 11 and an extension portion 15. The seal portion 11 has a tubular shape as a whole, and annular inner peripheral lips 12 are formed in a projected manner on an inner peripheral surface of the seal portion over its entire periphery, and are disposed at two axially-spaced positions, respectively. The inner diameter of the inner peripheral lips 12 is slightly smaller than the outer diameter of the wire 6. When the seal portion 11 is fitted on the wire 6, the inner peripheral lips 12 are elastically deformed and pressed against an outer periphery of a covering of the wire 6, so that a water-tight seal is formed between the inner periphery of the seal portion 11 and the outer periphery of the wire 6. Annular outer peripheral lips 13 are formed in a projected manner on the outer peripheral surface of the seal portion 11 over its entire periphery, and are disposed at two axially-spaced positions, respectively. The outer diameter of the outer peripheral lips 13 is slightly larger than the inner diameter of the cavity 2. When the seal portion 11 is inserted in the cavity 2, the outer peripheral lips 13 are elastically deformed and pressed against the inner peripheral surface of the cavity 2, so that a water-tight seal is formed between the outer periphery of the seal portion 11 and the inner periphery of the cavity 2. The extension portion 15 has a tubular shape as a whole, and extends rearwardly from the seal portion 11, that is, toward the open end 3 of the cavity 2 when the rubber plug 10 is inserted in the cavity. The extension portion 15 is formed integrally with the seal portion 11 by molding. The length of the extension portion 15 is dimensioned so that when the rubber plug 10 is inserted in the cavity 2, an extension end portion 16 of the extension portion 15 projects outwardly a predetermined distance from the open end 3 of the cavity 2. The outer diameter of the extension portion 15 is slightly smaller than the inner diameter of the cavity 2, and when the rubber plug 10 is inserted into the cavity 2, a slight gap 17 is formed between the inner periphery of the cavity 2 and the outer periphery of the extension portion 15. The inner diameter of the extension portion 15 is slightly larger than the outer diameter of the wire 6, and when the rubber plug 10 is fitted on the wire 6, a slight gap 18 is formed between the outer periphery of the wire 6 and the inner periphery of the extension portion 15. Next, the operation of this first embodiment will be described. When the rubber plug 10 is to be fitted on the wire 6, the wire 6 is passed through the rubber plug 10 against a frictional resistance produced as a result of pressing of the inner peripheral lips 12 of the seal portion 11 against the outer periphery of the wire 6. At this time, because the inner diameter of the extension portion 15 is larger than the outer diameter of the wire 6, a frictional resistance will not develop between the extension portion 15 and the wire 6. Therefore, the frictional resistance is kept to a minimum as a whole, thus reducing the time and labor required for assembly. The rubber plug 10 is thus fitted on the wire 6, which connects to the metal terminal 5. The rubber plug 10 is forced into the cavity 2, while holding the extension portion 15 by hand. At this time, the assembly is forced into the cavity against the frictional resistance produced as a result of pressing of the outer peripheral lips 13 of the seal portion 11 against the inner periphery of the cavity 2. However, because the outer diameter of the extension portion 15 is smaller than the inner diameter of the cavity 2 to provide the gap 17 therebetween, no frictional resistance develops between the outer periphery of the extension portion 15 and the inner periphery of the cavity 2. Thus, the only source of frictional resistance is the contact between the outer peripheral lips 13 of the seal portion 11 and the inner periphery of the cavity 2. Therefore, the overall frictional resistance is reduced. Therefore, very little time and labor will be required in the inserting operation, and the inserting operation can be carried out quite efficiently. Moreover, because the extension portion 15 has such a length that it projects from the open end 3 of the cavity 2 when the rubber plug 10 is mounted in position, the inserting operation can be done while holding the extension portion 15 by hand until the metal terminal 5 is inserted into a proper position. Throughout the inserting operation, the wire 6 need not be held by hand for insertion purposes. Therefore, buckling of the wire 6, which could occur when effecting the insertion by holding the wire by hand, is avoided. In addition, the efficiency of the operation is higher than the case where the insertion is effected by holding the wire 6 by hand. The rubber plug 10 is inserted into the cavity 2, and in this condition, when a bending force acts on the wire 6, a portion of the extension portion 15 disposed at and near the open end 3 of the cavity 2 is pressed by the wire 6 at a region disposed inwardly of the bent portion. Accordingly, the portion of the extension portion 15 is clamped between the edge of the open end 3 of the cavity 2 and the wire 6 to be elastically deformed, as shown in Fig. 2. At a region disposed outwardly of the bent portion, the wire 6 is disengaged from the inner periphery of the extension portion 15, and the extension portion 15 is elastically deformed away from the inner periphery of the cavity 2. Because the gap 17 between the extension portion 15 and the cavity 2, and the gap 18 between the extension portion 15 and the wire 6 are small, the amount of elastic deformation of the extension portion 15, and the amount of bending of the wire 6 in the extension portion 15 are also small. Therefore, that portion of the wire 6 received in the seal portion 11 only slightly bends. The bending force acting on the wire 6 will not be exerted on the seal portion 11, and the seal portion will not be elastically deformed. Therefore, the condition in which the outer peripheral lips 13 of the seal portion 11 are pressed in contact with the inner periphery of the cavity 2, as well as the condition in which the inner peripheral lips 12 are pressed in contact with the outer periphery of the wire 6, is maintained, and the sealing function is not damaged. Accordingly, water is prevented from entering the cavity 2 from the open end 3 and the metal terminal 5. Moreover, the wire 6 extends from the extension end portion 16 of the extension portion 15 that projects outwardly from the open end 3 of the cavity 2. Therefore, when a bending force acts on the wire 6, the wire 6 will not engage the edge of the open end 3 of the cavity, thereby avoiding a situation in which the wire 6 engages with and is rubbed by the edge of the open end 3 of the cavity 2 with the result that the covering of the wire 6 is damaged to expose a conductor of the wire. Next, a second preferred embodiment of the present invention will be described with reference to Fig. 3. A rubber plug 20 of the second embodiment comprises a seal portion 21, and an extension portion 25. Outer peripheral lips 23 and inner peripheral lips 22 of the seal portion 21 are pressed against an inner periphery of a cavity 2 and an outer periphery of a wire 6, respectively, thereby maintaining a water-tight sealed condition. The outer diameter of the extension portion 25 is slightly smaller than the inner diameter of the cavity 2, and the inner diameter of the extension portion is slightly larger than the outer diameter of the wire 6. In this embodiment, as in the seal portion 21, inner peripheral lips 22 are also formed on the inner periphery of the extension portion 25, and the inner peripheral lips 22 of the extension portion 25 are pressed against the outer periphery of the wire 6. Thus, the inner peripheral lips 22 are pressed in contact with the wire 6 at both the seal portion 21 and the extension portion 25. Therefore, when the wire 6 is bent, the close contact between the wire 6 and some of the inner peripheral lips 22 of the extension portion 25 is maintained even at a region disposed outwardly of the bent portion, thus providing a more positive sealing function. The invention has been described in detail with reference to preferred embodiments thereof, which are intended to be illustrative but not limiting. For example, the cavity is defined as having an inner diameter and the extension is defined as having an outer diameter, when the invention is applicable to cavities or extensions of any shape (e.g., square or rectangular) where an inner dimension of the cavity is larger than an outer dimension of the extension. Various changes may be made without departing from the invention as defined in the following appended claims.

Claims: A rubber plug in combination with a waterproof connector having a housing (1) that includes a cavity (2) including an inner surface, said rubber plug (10; 20) comprising: a seal portion (11; 21) that contacts the inner surface of the cavity (2) and an exterior surface of a wire (6) disposed within the rubber plug (10; 20); and an extension portion (15; 25) extending from said seal portion (11; 21) toward an open end (3) of said cavity (2), wherein a gap (17) is formed between the outer periphery of said extension portion (15; 25) and the inner surface of said cavity (2), characterized in that said extension portion (15; 25) has a length that projects outwardly from the open end (3) of said cavity (2). The rubber plug of claim 1, wherein the seal portion (11; 21) includes interior lips (12; 22) that form a waterproof seal between the wire (6) and an inner portion of the seal portion (11; 21), and exterior lips (13; 23) that form a waterproof seal between the inner surface of the cavity (2) and an outer portion of the seal portion (11; 21). The rubber plug of claim 1 or 2, wherein the extension portion (25) includes at least one interior lip (22) that forms a waterproof seal between the wire (6) and the interior portion of the extension portion (25). The rubber plug of claim 2 or 3, wherein at least one of the extension portion interior lips (22) and the seal portion interior lips (12; 22) maintain contact with the wire (6) despite application of a bending force to the wire (6). The rubber plug of anyone of claims 1 to 4, wherein the extension portion (15; 25) prevents the wire (6) from contacting an edge located near the open end (3) of the cavity (2). The rubber plug of anyone of claims 1 to 5, wherein an inner dimension of the extension portion (15; 25) is larger than an outer dimension of the wire (6) to define a space (18) between the extension portion (15; 25) and the wire (6). The rubber plug of anyone of claims 2 to 6, wherein a bending force applied to the wire (6) will cause the extension portion (15; 25) to contact the inner surface of the cavity (2) thereby enabling said exterior lips (13; 23) of the seal portion (11; 21) to maintain contact with the entire periphery of the inner surface of the cavity (2) to maintain a waterproof seal.

Inventors: ONOUE HISAYOSHI, TAKAHASHI MAKOTO, ONOUE, HISAYOSHI, TAKAHASHI, MAKOTO, ONOUE, HISAYOSHI, C/O SUMITOMO WIRING SYSTEMS, LTD, TAKAHASHI, MAKOTO, C/O SUMITOMO WIRING SYSTEMS LTD
Applicants: SUMITOMO WIRING SYSTEMS, SUMITOMO WIRING SYSTEMS, LTD.
Application year: 1994
Main classification: H01R13
IPC codes: H01R13